Neuroprotective effect of topically applied brimonidine tartrate 0.2% in endothelin-1-induced optic nerve ischaemia model

Background: To investigate the neuroprotective effects of topically applied brimonidine tartrate 0.2% (BMD), an α2‐receptor agonist, on the retinal ganglion cell (RGC) layer and inner nuclear layer (INL) of rabbit retina in endothelin‐1 (ET‐1)‐induced optic nerve (ON) ischaemia model. Methods: Osmotic minipumps were surgically implanted into one eye of 16 New Zealand Albino rabbits to deliver ET‐1 at the constant rate of 0.5 μL/h for 2 weeks. Eyes were divided into four groups. ET‐1 was given with (Group 3) and without topical BMD therapy (Group 1). Groups 2 and 4 were taken as controls. Rabbits were sacrificed at day 14. Morphological alterations, total cell number and proportion of cells undergoing apoptosis in INL and RGC layer were assessed by histopathological analysis to determine the survival of the cells of the INL and RGC layer. Results: Endothelin‐1 led to severe reduction of cells in both the RGC layer and INL in Group 1 (P